Osteonecrosis of the jaws caused by bisphosphonate treatment and oxidative stress in mice

Ozone therapy effect in medication-related osteonecrosis of the jaw as prevention or treatment: microtomographic, confocal laser microscopy and histomorphometric analysis

OBJECTIVE

This study aimed to evaluate the efficacy of ozone therapy in the preoperative (prevention) and/or postoperative (treatment) of MRONJ.

MATERIAL AND METHODS

Forty male Wistar rats were caudally treated with zoledronic acid (ZOL) and to ozone therapy before extraction (prevention, POG), after extraction (treatment, TOG), or both (prevention and treatment, TPOG), and treated with saline (SAL). The animals received intramuscular fluorochrome (calcein and alizarin), and 28 days postoperatively, they were euthanized, and the tissues were subjected to microtomographic computed tomography (microCT), LASER confocal, and histomorphometric analyses.

RESULTS

Micro-CT showed a higher bone volume fraction average in all groups than that in the ZOL group (P < 0.001), the ZOL group showed high porosity (P = 0.03), and trabecular separation was greater in the TOG group than in the POG group (P < 0.05). The mineral apposition rate of the POG group was high (20.46 ± 6.31) (P < 0.001), followed by the TOG group (20.32 ± 7.4). The TOG group presented the highest mean newly formed bone area (68.322 ± 25.296) compared with the ZOL group (P < 0.05), followed by the SAL group (66.039 ± 28.379) and ZOL groups (60.856 ± 28.425).

CONCLUSIONS

Ozone therapy modulated alveolar bone repair in animals treated with ZOL, mainly after surgery trauma, leading to bone formation as healing tissue.

CLINICAL RELEVANCE

Osteonecrosis has been a challenge in dentistry, and owing to the lack of a consensus regarding therapy, studies presenting new therapies are important, and ozone has been one of the therapies explored empirically.

G‑CSF delays tooth extraction socket bone healing via the inhibition of bone turnover in mice

Granulocyte colony-stimulating factor (G-CSF) regulates the survival, proliferation and differentiation of all cells in the neutrophil lineage, and is consequently used for neutropenic conditions. Upon G-CSF administration, osteoblasts and osteocytes are suppressed, and the support system allowing hematopoietic stem cells to remain in the microenvironment is diminished. The present study focused on and investigated G-CSF as a regulatory factor of bone remodeling. The aim of the present study was to investigate the effect of G-CSF administration on the bone healing of tooth extraction sockets. Significant differences in the bone volume fraction, and trabecular separation of the proximal femurs and alveolar septa were observed between the G-CSF and control (saline-treated) groups. The trabecular bone of the femur and alveolar septa was reduced in the G-CSF group compared with that in the control group. In addition, serum procollagen type 1 N-terminal propeptide levels, a marker of bone formation, were lower in the G-CSF group compared with in the control group. Fibrous connective tissues and immature bone were observed in the extraction socket, and bone healing was delayed in the G-CSF group compared with that in the control group. The bone area in the extraction socket 6 days after tooth extraction was significantly smaller in the G-CSF group (23.6%) than that in the control group (45.1%). Furthermore, G-CSF administration reduced the number of canaliculi per osteocyte and inhibited the connection of osteocyte networks. Consequently, osteoblast activation was inhibited and bone remodeling changed to a state of low bone turnover in the G-CSG group. Analysis of bone formation parameters revealed that the G-CSF group exhibited a lower mineral apposition rate compared with in the control group. In conclusion, these findings indicated that G-CSF may delay bone healing of the socket after tooth extraction.

Conditioned Medium from Bone Marrow Mesenchymal Stem Cells Restored Oxidative Stress-Related Impaired Osteogenic Differentiation

Oxidative stress from high levels of intracellular reactive oxygen species (ROS) has been linked to various bone diseases. Previous studies indicate that mesenchymal stem cells (MSC) secrete bioactive factors (conditioned medium (MSC-CM)) that have antioxidant effects. However, the antioxidant role of MSC-CM on osteogenesis has not been fully studied. We aimed to identify antioxidant proteins in MSC-CM using mass spectrometry-based proteomics and to explore their effects on osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSC) exposed to oxidative stress induced by hydrogen peroxide (H₂O₂). Our analysis revealed that MSC-CM is comprised of antioxidant proteins that are involved in several biological processes, including negative regulation of apoptosis and positive regulation of cell proliferation. Then, hBMSC exposed to H₂O₂ were treated with MSC-CM, and the effects on their osteogenic differentiation were evaluated. MSC-CM restored H₂O₂-induced damage to hBMSC by increasing the antioxidant enzyme-SOD production and the mRNA expression level of the anti-apoptotic BCL-2. A decrease in ROS production and cellular apoptosis was also shown. MSC-CM also modulated mRNA expression levels of osteogenesis-related genes, runt-related transcription factor 2, collagen type I, bone morphogenic protein 2, and osteopontin. Furthermore, collagen type I protein secretion, alkaline phosphatase activity, and in vitro mineralization were increased. These results indicate that MSC-CM contains several proteins with antioxidant and anti-apoptotic properties that restored the impaired hBMSC osteogenic differentiation associated with oxidative stress.

Various Therapeutic Methods for the Treatment of Medication-Related Osteonecrosis of the Jaw (MRONJ) and Their Limitations: A Narrative Review on New Molecular and Cellular Therapeutic Approaches

Medication-related osteonecrosis of the jaw (MRONJ) is one of the most interesting diseases in the field of maxillofacial surgery. In addition to bisphosphonates, the use of antiresorptive and antiangiogenic agents is known to be the leading cause. However, the exact pathogenesis of MRONJ has not been established, and various hypotheses have been proposed, such as oxidative stress-related theory. As a result, a definitive treatment protocol for MRONJ has not been identified, while various therapeutic approaches are applied to manage patients with MRONJ. Although the surgical approach to treat osteomyelitis of the jaw has been proven to be most effective, there are limitations, such as recurrence and delayed healing. Many studies and clinical trials are being conducted to develop another effective therapeutic modality. The use of some materials, including platelet concentrates and bone morphogenetic proteins, showed a positive effect on MRONJ. Among them, teriparatide is currently the most promising material, and it has shown encouraging results when applied to patients with MRONJ. Furthermore, cell therapy using mesenchymal stem cells showed promising results, and it can be the new therapeutic approach for the treatment of MRONJ. This review presents various treatment methods for MRONJ and their limitations while investigating newly developed and researched molecular and cellular therapeutic approaches along with a literature review.

Mitigating osteonecrosis of the jaw (ONJ) through preventive dental care and understanding of risk factors

It is well established that alterations in phosphate metabolism have a profound effect on hard and soft tissues of the oral cavity. The present-day clinical form of osteonecrosis of the jaw (ONJ) was preceded by phosphorus necrosis of the jaw, ca. 1860. The subsequent removal of yellow phosphorus from matches in the early 20th century saw a parallel decline in "phossy jaw" until the early 2000s, when similar reports of unusual jaw bone necrosis began to appear in the literature describing jaw necrosis in patients undergoing chemotherapy and concomitant steroid and bisphosphonate treatment. Today, the potential side effect of ONJ associated with medications that block osteoclast activity (antiresorptive) is well known, though the mechanism remains unclear and the management and outcomes are often unsatisfactory. Much of the existing literature has focused on the continuing concerns of appropriate use of bisphosphonates and other antiresorptive medications, the incomplete or underdeveloped research on ONJ, and the use of drugs with anabolic potential for treatment of osteoporosis. While recognizing that ONJ is a rare occurrence and ONJ-associated medications play an important role in fracture risk reduction in osteoporotic patients, evidence to date suggests that health care providers can lower the risk further by dental evaluations and care prior to initiating antiresorptive therapies and by monitoring dental health during and after treatment. This review describes the current clinical management guidelines for ONJ, the critical role of dental-medical management in mitigating risks, and the current understanding of the effects of predominantly osteoclast-modulating drugs on bone homeostasis.